This invention relates to a method for forming a conductive graphite film having high conductivity and the same obtained by the method.
The so-called thermal decomposition method is conventionally employed to obtain graphitized carbon. That method comprises thermally decomposing hydrocarbon by heating reacting material to high temperatures in an atmosphere of hydrocarbon as raw material to form carbon materials (for instance, "Foundation of Carbonization Engineering", Ohtani, 1980, Ohom)(Method 1). The carbon materials are roughly divided into three kinds shown in Table 1 ([Introduction to Carbon Material], Nagaoki, 1979, Society of Carbon Material). The conductivity of graphite A at normal temperatures is 2.5.about.5.times.10.sup.3 S/cm.
TABLE 1 ______________________________________ Kinds of Production Principal graphites: temperature: (.degree.C.) properties: ______________________________________ A 2,000.about.2,200 high density, high anisotropy B 1,500.about.1,700 low density, low anisotropy C 1,200.about.1,400 low density, low anisotropy (low formation speed) ______________________________________
It is well known to graphitize the carbon material thus obtained through the above-described method by subjecting it to heat treatment at a high temperature of, for instance, 3,000.degree. C.
Another conventional method often employed comprises carrying out the plasma polymerization of benzene by means of a high-frequency discharge at temperatures lower (1,000.degree. C.) than those in the above-described method to obtain a thin carbon film on a quartz plate or silicon wafer (H. MATSUSHIMA et al, J. APPL. PHYS. Vol. 22 (No. 5), 888 (1982)) (Method 2).
In the above-described method 1, however, a thermal decomposition temperature of 2,000.degree. C. or higher is required as a condition for obtaining high conductive graphitized carbon. Kinds of substrate materials at such high temperatures are limited and energy loss is also large. Accordingly, the formation of graphitized carbon at low temperatures is being desired.
In the method 2, conductivity is less than 10.sup.3 S/cm, whereas the growth rate of carbon material is 0.052 .mu.m/min, which is extremely low as compared with the growth rate of carbon material (1.7.about.17 .mu.m/min) in accordance with the heat decomposition method in the method 1.